Anisotropic mechanical behavior of Zincblende and Wurtzite indium phosphide nanowires

Of late, indium phosphide (InP) nanowires (NWs) have garnered significant attention as foundational components for next-generation nanoelectronics, optoelectronics, and electromechanical devices, owing to their exceptional semiconducting and optical properties. Nevertheless, the practical integration of InP NWs remains hindered by the difficulty in precisely tailoring crystal orientation and mitigating intrinsic vacancy defects, both of which play a pivotal role in determining their mechanical performances. This work employs atomistic molecular dynamics simulations to systematically elucidate the influence of crystallographic orientation, size, temperature, and vacancy defects on the tensile mechanical behavior and deformation mechanisms of zincblende (ZB) and wurtzite (WZ) InP NWs. The results show significant anisotropy in mechanical response: ZB [111] NWs exhibit the highest elastic modulus (∼107 GPa) and fracture strength (∼8.3 GPa), whereas [100] NWs demonstrate superior ductility and fracture toughness. For WZ NWs, the [0001] orientation exhibits superior elastic modulus and strength compared to the [01−10] orientation. Elevated temperatures (100–600 K) anisotropically degrade the mechanical strength of ZB and WZ InP NWs, driven by orientation-dependent surface energy, interatomic spacing, and coordination. Vacancy defects—especially indium vacancies—significantly reduce the fracture stress (up to ∼31%) while the elastic modulus is found to be more sensitive to the removal of phosphorus atoms (up to ∼10% reduction) due to 1% vacancy. Orientation-dependent sensitivity to vacancy defects is evident: ZB [100] NWs exhibit the greatest reduction in elastic modulus, while [111] NWs are most susceptible to fracture strength degradation; conversely, WZ [01−10] NWs show pronounced stiffness loss, whereas [0001] NWs retain greater mechanical robustness. At low temperatures, failure in ZB InP NWs predominantly occurs along the {111} slip planes. However, at elevated temperatures, additional cleavage planes such as {100} become active due to increased bond instability and reduced interplanar spacing, leading to fracture at lower strain levels. This study provides an atomistic-level understanding of the interplay between crystal orientation, temperature, and defect conditions on the mechanical performance of InP NWs, offering critical design guidelines for high-performance and robust nanodevices. • Atomistic MD study reveals anisotropic tensile behavior in ZB and WZ InP nanowires. • ZB [111] and WZ [0001] show the highest strength; ZB [100] offers superior toughness. • Mechanical properties degrade anisotropically with increasing temperature. • Indium and phosphorus vacancies reduce fracture strength and modulus differently. • Temperature and defects alter slip activation and fracture mechanisms in InP NWs.